Beam dampers for damping the vibrations of the skin of reinforced structures

Abstract

Beam dampers comprising a stiff, lightweight, elongate beam and layer of viscoelastic material located along an attachment flange of the beam are disclosed. The flanges of the beam is attached by the layer of viscoelastic material to the skin of a structure whose skin vibrations are to be damped. While a beam having a cross-sectional I-shape is preferred, other cross-sectional shapes can be used, such as L, Z, U and T-shapes. Regardless of their shapes, the beam acts as a constraining element for the viscoelastic attachment layer. The beam is oriented such that it is stiff in a plane transverse to the plane of the skin, resulting in thickness deformation of the layer of viscoelastic material (rather than shear deformation) converting vibration energy into heat.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows: 
     
       1. In a reinforced skin structure, wherein a skin is supported by spaced apart reinforcing elements, the improvement comprising: beam dampers attached to said skin between said reinforcing elements for damping vibrations of said skin, each of said beam dampers including: a stiff, lightweight elongate beam formed so as to resist bending in at least one plane and including an attachment plate lying orthogonal to said at least one plane; and,   a layer of material that converts vibration energy into heat when deformed by vibration, said material located on one face of said attachment plate of said beam for attaching said plate to said skin such that said at least one plane in which said beam resists bending lies transverse to said skin, resulting in a thickness deformation of said layer of material when said skin vibrates, said thickness deformation of said layer of material converting vibration energy into heat to damp said skin vibration.   
     
     
       2. The improvement claimed in claim 1 wherein said material that converts vibration energy into heat when deformed by vibration is a viscoelastic material. 
     
     
       3. The improvement claimed in claim 2 wherein said stiff, lightweight elongate beam has an I-shaped cross-sectional configuration and wherein said layer of viscoelastic material is located on the outer face of one of the flanges of said I-shape beam, said flange forming said attachment plate. 
     
     
       4. The improvement claimed in claim 3 wherein said reinforcing elements lie parallel to one another and wherein said beam dampers lie parallel to said reinforcing elements. 
     
     
       5. The improvement claimed in claim 3 wherein said reinforcing elements lie parallel to one another and wherein said beam dampers lie orthogonal to said reinforcing elements. 
     
     
       6. The improvement claimed in claim 3 including a layer of damping tape comprising a layer of viscoelastic material and a thin reinforcing layer positioned between said viscoelastic layer located on said one face of said flange of said I-shaped beam and said skin. 
     
     
       7. The improvement claimed in claim 3 including an overlying reinforcing strip and viscoelastic attachment layers for attaching said overlying reinforcing strip to the other flange of said I-shaped beam and to said reinforcing element. 
     
     
       8. The improvement claimed in claim 3 wherein one flange of said I-shaped beam is wider than the other and wherein said layer of viscoelastic material is located on said wider flange of said I-shaped beam. 
     
     
       9. The improvement claimed in claim 3 wherein said stiff, lightweight elongate beam is formed of metal. 
     
     
       10. The improvement claimed in claim 3 wherein said stiff, lightweight elongate beam is formed of a nonmetallic material. 
     
     
       11. The improvement claimed in claim 10 wherein said nonmetallic material is a high strength-to-weight ratio synthetic material. 
     
     
       12. The improvement claimed in claim 2 wherein said reinforcing elements lie parallel to one another and wherein said beam dampers lie parallel to said reinforcing elements. 
     
     
       13. The improvement claimed in claim 2 wherein said reinforcing elements lie parallel to one another and wherein said beam dampers lie orthogonal to said reinforcing elements. 
     
     
       14. The improvement claimed in claim 2 including a layer of damping tape comprising a layer of viscoelastic material and a thin reinforcing layer positioned between said viscoelastic layer located on said one face of said attachment plate and said skin. 
     
     
       15. The improvement claimed in claim 2 wherein said stiff, lightweight elongate beam has a T-shaped cross-sectional configuration and wherein said layer of viscoelastic material is located on the outer surface of the cross-member of said T-shaped beam, said cross-member forming said attachment plate. 
     
     
       16. The improvement claimed in claim 15 wherein said stiff, lightweight elongate beam is formed of metal. 
     
     
       17. The improvement claimed in claim 15 wherein said stiff, lightweight elongate beam is formed of a nonmetallic material. 
     
     
       18. The improvement claimed in claim 17 wherein said nonmetallic material is a high strength-to-weight ratio synthetic material. 
     
     
       19. The improvement claimed in claim 2 wherein said stiff, lightweight, elongate beam has an L-shaped cross-sectional configuration and wherein said layer of viscoelastic material is located on the outer face of one flange of said L-shaped beam, said one flange forming said attachment plate. 
     
     
       20. The improvement claimed in claim 19 wherein said stiff, lightweight elongate beam is formed of metal. 
     
     
       21. The improvement claimed in claim 19 wherein said stiff, lightweight elongate beam is formed of a nonmetallic material. 
     
     
       22. The improvement claimed in claim 21 wherein said nonmetallic material is a high strength-to-weight ratio synthetic material. 
     
     
       23. The improvement claimed in claim 2 wherein said stiff, lightweight elongate beam has a U-shaped cross-sectional configuration and wherein said layer of viscoelastic material is located on the outer face of the cross-member of said U-shaped beam, said cross-member forming said attachment plate. 
     
     
       24. The improvement claimed in claim 23 wherein said stiff, lightweight elongate beam is formed of metal. 
     
     
       25. The improvement claimed in claim 23 wherein said stiff, lightweight elongate beam is formed of a nonmetallic material. 
     
     
       26. The improvement claimed in claim 25 wherein sid nonmetallic material is a high strength-to-weight ratio synthetic material. 
     
     
       27. The improvement claimed in claim 2 wherein said stiff, lightweight elongate beam has a Z-shaped cross-sectional configuration and wherein said layer of viscoelastic material is located on the outer face of one of the flanges of said Z-shaped beam, said one of the flanges forming said attachment plate. 
     
     
       28. The improvement claimed in claim 27 wherein said stiff, lightweight elongate beam is formed of metal. 
     
     
       29. The improvement claimed in claim 27 wherein said stiff, lightweight elongate beam is formed of a nonmetallic material. 
     
     
       30. The improvement claimed in claim 29 wherein said nonmetallic material is a high strength-to-weight ratio synthetic material.